[Bug c++/91264] modifying const-qual object in constexpr context not detected

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91264

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Another test:

constexpr void
f (int &r)
{
  r = 99;
}

constexpr int
f2 ()
{
  const int i = 0;
  f (const_cast<int&>(i));
  return i;
}

constexpr int i = f2 ();